1. Field of the Invention
The present invention relates, in general, to digital hearing aids, and, more particularly, to a digital hearing aid adaptive to the structures of human external ear canals, which models the structures of external ear canals, the sizes and shape characteristics of which differ between respective persons, captures resonance gains occurring due to the structural characteristics thereof, and performs digitization and signal processing on the resonance gains to allow the resonance gains to be used as gain factors, thus optimizing the performance of the digital hearing aid in consideration of personal features.
2. Description of the Related Art
The hearing of sound has a meaning beyond a simple sensory action. When hearing ability is lost, it is impossible to normally perform social activity, and, as a result, feeble-mindedness may occur. A hearing aid, which is a tool used to compensate for hearing impairment occurring due to the loss of hearing ability, aims to amplify an acoustic signal, input to the hearing organ of a person who has difficulty in hearing, to thus make the amplitude of the acoustic signal, recognized through the brain, the same as that of a normal person.
Hearing aids, currently being commercialized, can be mainly classified into three types, that is, an analog type, a digital type, and an analog/digital hybrid type.
Analog hearing aids, currently occupying most hearing aid markets, have been greatly developed over the past several decades from the standpoint of functionality, but possible signal processing methods are inevitably limited to basic items in such a way that the audible range is compressed or amplified using a limited number of bands (typically, two or three bands). This is due to problems in that an analog circuit has low flexibility or reliability and in that it is difficult to implement a complicated signal processing method because the adjustment of functions is not facilitated.
Therefore, the necessity for digital hearing aids having a digital circuit therein has existed for a long period of time, and the development of digital signal processing algorithms required for the digital hearing aids has also been continuously conducted.
Digital hearing aids can easily realize a complicated high-performance signal processing algorithm while realizing an advantage in circuit flexibility and reliability, and, in particular, can efficiently implement a high-performance hearing impairment compensation algorithm, such as a non-linear correction method for patients undergoing autoimmune sensorineural hearing loss.
However, typical digital hearing aids do not take inherent resonance gains of personal external ear canals into account during a gain fitting and verification process, but extract and fit gains only through a hearing test, and thus the degree of satisfaction of each individual, obtained through initial fitting, is greatly decreased.
Therefore, continuous post-fitting management is required, and both the time required for gain fitting and gain errors, occurring due to the continuous post-fitting management, greatly differ between respective persons, which becomes a principal factor making gain fitting difficult.
Typical methods of performing post-fitting management are classified into a probe-tube microphone fitting verification method and a functional gain fitting verification method.
However, in the case of the probe-tube microphone fitting verification method, there are problems in that a considerable error occurs in measured gains depending on the location of a probe-tube, and in that, since the motion of each individual is limited at the time of measurement, it is difficult to use this method for children. In the case of the functional gain fitting verification method, there are problems in that reliability is deteriorated at the time of retesting and in that resolution in a frequency domain is deteriorated.